Everyone should carry only fixed blades that cost < $10, and Moras can and indeed should be used to baton through Busse knives.
OK, now that that's out of my system, time to get serious:
I am of the opinion that you can get away with a small fixed blade for just about everything. My EDC is a pocket scandi with a 3" cutting edge and comfortable 3.5" handle. This knife gets used for food prep, making fuzz sticks, whittling, cleaning fish, wood notching, household tasks, opening boxes, etc. I can think of very few occasions over the last few months when I have actually
needed a larger blade. If you dropped me in the bush with just my EDC, I would probably feel totally under-knifed at first, but unless I needed to baton, chop, pry, hack through underbrush, or fend off sasquatch, I would probably do just fine.
Handle shape is key, as pitdog mentioned. I designed my EDC so that the blade is lower than the front fingers (to aid with cutting and particularly food prep), but with a wider rear end that fills the palm for comfort and grip. I added a few thumb notches to help with grip and control.
A knife of this size only falls short, in my opinion, in situations where you need to apply additional force, beyond what would normally be required to cut something (really, anything that involves taking a swing).
All that being said, I like the versatility of a 4-5" blade, as it can accomplish the same tasks as my EDC, but also perform reasonably well at some chopping, splitting, or batoning tasks.
All the best,
- Mike